I hate to say it but you probably shouldn't be installing iOS 8, which the beta was announced just over 24 hours ago, on a phone that you're worried about bricking.
If it's for development, you have a developer account, and something renders the in warranty iPhone broken then Apple will help you out. So no worries.
If you're just wanting to play with a shiny new OS and it's not a sure thing that Apple will help you if something goes wrong, then yeah, I wouldn't. At the very least wait for 2-3 beta releases from now.
With that said I'd side with jpetticrew, a hard reset will likely reset it and finish up the install. Worst case you just put it in DFU mode and restore/upgrade it again.